This invention relates to an earplug which can effectively reduce the amount of noise entering into the ears.
At the present time when the standard noise level at 2000 cps is generally considered to be approximately 70 to 80 phons, an earplug which has a noise interruption rate ranging from 40 to 50 phons will be sufficient to protect the labyrinth of the ear from "excessive sound" which may be of 110 to 120 phons.
A conventional earplug is constructed such that a straight elongated hole passes through the earplug body and the diameter of the hole is substantially large and furthermore, the earplug body is usually made of a plastic material.
Accordingly, the conventional plug suffers from the following disadvantages:
(I) The maximum noise interruption rate obtained by the above earplug is 40 db when the noise level exceeds 2000 cps.
This is explicitly shown in FIG. 4 which is a performance graph wherein the frequency of the sound is the abscissa and the noise interruption rate is on the ordinate.
(II) Since the material of the earplug is plastic, a person who wears the earplugs feels uncomfortable and becomes fatigued with their extended use.